For writers who want to break into graphic novels, I think it’s worth your while to pay an artist to illustrate a short comic that you can make available as a chapbook to sell or give away. Yes, it’s an investment, but it accomplishes two important things:

It’s an introduction for you to what it’s like to work with an artist. Anything you find challenging about collaborating on a short story will only be magnified when you work on a full-length graphic novel. Better to learn on a shorter-term project, so you can use what you’ve learned to make whatever changes in your work style will make the graphic novel collaboration process more successful.

You’ll have something tangible to hand to editors at conventions that they can read through quickly to assess your work. (Caveat: not that they’re likely to do so while you’re standing there.)